Effect of photosensitizer diethylamine on the photodegradation of polychlorinated biphenyls

The objective of this study was to investigate the effect of diethylamine and xenon simulated sunlight on the photodegradation of two forms of PCBs including PCBs in transformer oil and PCB congener 138. The result of GC chromatograms illustrated the shifting pattern of higher chlorinated biphenyls in transformer oil degraded to lower chlorinated biphenyls with the extension of exposure time. The effect of diethylamine and xenon simulated sunlight was significant on the photodegradation of both PCBs in transformer oil and congener 138. The initial degradation rates of congener 138 (1.14 x 10(-9) to 4.47 x 10(-9) mol l(-1) h(-1)) were in direct proportion to the initial concentrations of congener 138 which confirmed the pseudo-first-order reaction of PCB photodegradation. The apparent quantum yields (phi) of congener 138 using diethylamine in xenon photoreactor were ranged between 2.08 x 10(-2) and 9.8 x 10(-4). PCB congeners 123, 97, 70, 67, 33, 29, 17, 12, and 9 were detected as the descendants of the photodegradation of congener 138 through dechlorination. The major pathway of congener 138 photodegradation in this study was via para-dechlorination.     

复合催化氧化技术对油气田压裂返排液的处理研究

酸化压裂作业废水是石油天然气生产过程中的主要污染源,它的污染成份复杂,有害物质浓度高,特别是含有胍胶和表面活性剂等高分子物质,具有高COD、高稳定度、高粘度的特点.本文通过对压裂液的来源、水质特征、治理现状等常用方法的分析,确定了物理化学脱稳,过滤、O3/H2O2复合催化氧化、深度氧化的达标治理工艺路线.经过处理后的压裂液澄清透明,达到国家二级排放标准(GB8978-96).     

Seasonal temperatures have more influence than nitrogen fertilizer rates on cucumber yield and nitrogen uptake in a double cropping system

Two-year greenhouse cucumber experiments were conducted to investigate seasonal effects on fruit yield, dry matter allocation, and N uptake in a double-cropping system with different fertilizer management. Seasonal effects were much greater than fertilizer effects, and winter-spring (WS) cucumber attained higher fruit yields and N uptake than autumn-winter (AW) cucumber due to lower cumulative air temperatures during fruit maturation in the AW season. Fertilizer N application and apparent N loss under recommended N management (Nmr) decreased by 40-78% and 33-48% without yield loss compared to conventional N management (Nmt) over four growing seasons. However, there were no seasonal differences in N recommendations, taking into consideration seasonal differences in crop N demand, critical nutrient supply in the root zone and N mineralization rate.     

Recycling of municipal solid waste incinerator fly ash by using hydrocyclone separation

The municipal solid waste incinerators (MSWIs) in Taiwan generate about 300,000 tons of fly ash annually, which is mainly composed of calcium and silicon compounds, and has the potential for recycling. However, some heavy metals are present in the MSWI fly ash, and before recycling, they need to be removed or reduced to make the fly ash non-hazardous. Accordingly, the purpose of this study was to use a hydrocyclone for the separation of the components of the MSWI fly ash in order to obtain the recyclable portion. The results show that chloride salts can be removed from the fly ash during the hydrocyclone separation process. The presence of a dense medium (quartz sand in this study) is not only helpful for the removal of the salts, but also for the separation of the fly ash particles. After the dense-medium hydrocyclone separation process, heavy metals including Pb and Zn were concentrated in the fine particles so that the rest of the fly ash contained less heavy metal and became both non-hazardous and recyclable.     

Impact of chemical leaching on permeability and cadmium removal from fine-grained soils

The aim of this study was to investigate the influence of chemical leaching on permeability and Cd removal from fine-grained polluted soils. Column leaching experiments were conducted using two types of soils (i.e., artificially Cd-polluted loam and historically polluted silty loam). Chemical agents of CaCl₂, FeCl₃, citric acid, EDTA, rhamnolipid, and deionized water were used to leach Cd from the soils. Results showed that organic agents reduced permeability of both soils, and FeCl₃ reduced permeability of loam soil, compared with inorganic agents and deionized water. Entrapment and deposition of colloids generated from the organic agents and FeCl₃ treatments reduced the soil permeability. The peak Cd effluence from the artificially polluted loam columns was retarded. For the artificially polluted soils treated with EDTA and the historically polluted soils with FeCl₃, Cd precipitates were observed at the bottom after chemical leaching. When Cd was associated with large colloid particles, the reduction of soil permeability caused Cd accumulation in deeper soil. In addition, the slow process of disintegration of soil clay during chemical leaching might result in the retardation of peak Cd effluence. These results suggest the need for caution when using chemical-leaching agents for Cd removal in fine-grained soils.

     

Photoelectrocatalytic degradation of pentachlorophenol in aqueous solution using a TiO2 nanotube film electrode

Titanium dioxide (TiO2) nanotube film electrodes are fabricated by the anodic oxidation method. Scanning electron microscopy (SEM) showed that these tubes were well aligned and organized into high-density uniform arrays. XRD analysis showed the TiO2 nanotubes to be in the anatase crystal form. The TiO2 nanotube film electrode exhibited increased photoelectrocatalytic (PEC) capability compared to a traditional TiO2 film electrode fabricated using the anodizing method for pentachlorophenol (PCP) degradation in aqueous solution. The bias potential, pH value, and electrolyte concentration were shown to be important factors influencing the degradation of PCP by the PEC method using the TiO2 nanotube film electrode as the working electrode.     

Changes of copper speciation in maize rhizosphere soil

Chemical forms of copper in the rhizosphere and bulk soil of maize were investigated using rhizobox cultivation and sequential extraction techniques. The copper accumulations were also determined. The results demonstrated that there were continuous changes in copper fractionation within the maize rhizosphere. Initially, the amount of exchangeable copper increased before dropping below the initial level after 40 days or so. Carbonate associated copper followed a similar trend of change, but with a slower pace than the exchangeable copper. The increase in carbonate associated copper only become evident after 30 days, with the net loss occurring after 60 days. There were also initial increases in oxide bound copper as well as decreases in the organic matter associated copper, both followed by a turnover after 40-50 days. The accumulation of copper in the maize plant was found to be biomass dependent. The amount of accumulated copper absorbed in the plant material exceeded the initial quantity of the exchangeable copper in the soil, revealing a transformation from less bioavailable to more bioavailable fractions. During cultivation, decreases in redox potential and increases in pH, dissolved organic carbon (DOC), and microbial activity in the maize rhizosphere were observed. The change in copper speciation may result from root-induced changes in DOC, redox potential, and microbial activity in the rhizosphere.     

Reversed association between levels of prostate specific antigen and levels of blood cadmium and urinary cadmium

Prostate cancer associated with cadmium exposure may indicate a link between prostate specific antigen (PSA) and levels of blood cadmium (BCd) and urinary cadmium (UCd). Thus, these associations were investigated. We recruited 295 men, 50 years of age and above from a health check-up program at a health center as subjects of the study. They completed a self-reported questionnaire and provided fasting samples of blood and urine for cadmium assay. The assay was performed using atomic absorption spectrophotometry. Blood samples were also collected for the assays of total cholesterol and high-density lipoprotein measures. The means of BCd and UCd increased with age and the means of all subjects were 1.19 ± 1.04 μg L⁻¹ and 1.37 ± 1.76 μg g⁻¹ creatinine, respectively. The PSA levels were positively associated with the lipid levels, but reversely associated with BCd and UCd levels. The multivariate logistic regression analysis showed that men with PSA ? 4.0 ng mL⁻¹ had an odds ratio (OR) of 0.4 (95% CI = 0.1-0.9) to have BCd > 0.49 μg L⁻¹, and an OR of 0.4 (95% CI = 0.2-1.0) to have UCd > 0.45 μg g⁻¹ creatinine. In conclusion, the PSA levels are reversely associated with BCd and UCd levels.     

沸石颗粒在污泥絮体中的形态及其对污泥泥水分离的影响

投加沸石粉提高了活性污泥的泥水分离性能。通过对沸石颗粒表面生物膜和投加了沸石粉的活性污泥絮体生长过程及成熟形态的微观观察,结果表明沸石颗粒不仅可以作为微生物载体长成生物膜,而且成为菌胶团核心和污泥絮体骨架,改善了污泥絮体的颗粒结构,从而增强了絮体强度,提高了絮体密度,降低了污泥塑性。研究结果表明沸石粉适宜的投加量为4g/L;在活性污泥中投加4g/L沸石粉后,SVI从193降低到155,污泥比阻从27.36×1012m/kg降低到5.67×1012m/kg;在沸石粉含量小于10g/L时,随着沸石粉含量的增加,污泥呈现压缩沉淀时界面沉速和出现压缩沉淀的时间持续减小。